Comparing Carbonate and Organic Ams- 14 C Ages in Lake Abiyata Sediments (Ethiopia)

Hydrochemistry and Paleoenvironmental Implications

Bibliographic Data

ID9243431
AuthorsElisabeth Gibert, Yves Travi (0000-0002-6143-2355), Marc Massault, Tesfaye Chernet, Florent Barbecot (0000-0002-3286-3156), Fatima Laggoun-Defarge
Year1999
Volume41
Issue3
Pages271-286
Publication date1999-01-01
Open AccessYes
TypeARTICLE
VenueRadiocarbon (JOURNAL)
Journal identifiersISSN: 0033-8222 • E-ISSN: 1945-5755
PublisherCambridge University Press (CUP) (PUBLISHER)
DOI10.1017/s0033822200057131
OpenAlexW2282658379
LanguageEN
Citations received3
References cited18

We studied a 12.6-m-long sequence from Lake Abiyata (Central Ethiopia) to establish a reliable and accurate chronology for use in global paleoclimatic reconstructions. The 26 accelerator mass spectrometry radiocarbon (AMS 14 C) ages, performed on carbonates and organic matter, define 2 parallel chronologies, representing the complete Holocene period. However, these chronologies show a significant discrepancy from 500 to 900 BP in depth; ages obtained on carbonates were always older than those on organic matter. The hydrogeological and geochemical behavior of the Lake Abiyata basin has shed light on this discrepancy. We found that the carbonate crystallization is due mainly to the mixing of lake waters with groundwaters from the multi-layered aquifer contained in the 600-m-thick basement of the lake. The 14 C activity of total dissolved inorganic carbon (TDIC) measured by AMS from bottom and surface lake waters (111.4 and 111.8 pMC, respectively) confirms that the mixing occurs at the water-sediment interface. This evidence of groundwater participation in the carbonate crystallization calls into question the current paleoclimatic reconstructions based on inorganic carbonates in lakes. Specific attention should thus be given to the respective proportions of each end-member in the mixing for the quantitative estimation of the groundwater input. This will help to validate the paleoenvironmental reconstructions and to highlight an eventual diagenetical evolution of inorganic carbonates during burial, via the study of pore waters

Accelerator mass spectrometry · Carbonate · Dissolved organic carbon · Geochemistry · Groundwater · Radiocarbon dating · Sediment · Chemistry · Geology and Paleoclimatology Research · Groundwater and Isotope Geochemistry · Hydrocarbon exploration and reservoir analysis · Geology · Oceanography · Paleontology

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